1. Field of the Invention
The present invention relates to double-faced pressure-sensitive adhesive tapes that are thin and highly waterproof.
2. Description of the Related Art
Substrate-supported double-faced pressure-sensitive adhesive tapes (double-coated self-adhesive tapes) have been used for various purposes such as bonding and fixation. These substrate-supported double-faced pressure-sensitive adhesive tapes each include a substrate (carrier) and arranged on both sides thereof, pressure-sensitive adhesive layers (self-adhesive layers). Typically, some of them use, as the substrate, nonwoven fabrics (Japanese Unexamined Patent Application Publication No. 2001-152111), paper, or plastic films.
As the function of waterproofing has been required of cellular phones, substrate-supported double-faced pressure-sensitive adhesive tapes used for the fixation or fastening of components in such cellular phones should be waterproof (be sealable against water). The known substrate-supported double-faced pressure-sensitive adhesive tapes, however, fail to provide satisfactory waterproofness. Typically, nonwoven fabrics and paper, if used as a material for the substrate, are impregnated with water (absorb water) and the resulting substrate-supported double-faced pressure-sensitive adhesive tapes are inferior in waterproofness. Plastic films, if used as a material for the substrate, are relatively rigid, and the resulting substrate-supported double-faced pressure-sensitive adhesive tapes do not satisfactorily fit uneven or rough portions (portions differing in level), thereby suffer from gap in such uneven portions, and show unsatisfactory waterproofness.
In addition, such substrate-supported double-faced pressure-sensitive adhesive tapes should be reduced in thickness for the reduction in weight, size, and thickness of products in which the tapes are used. And, even when they are reduced in thickness, they should undergo processing satisfactorily.